Have you ever seen a solar oven in a backyard? Have you ever seen somebody cooking with a solar oven? Solar ovens would be an easy addition to everyday life that would save tons of money and gas resources. There are several types of solar ovens, and they are all fairly simple to make. They require a few household materials, and other materials found easily at your nearest hardware store.

Solar ovens work through a process called convection. Heat is trapped in the parts of a solar oven and then relayed back through the pot into the food. Depending on the type of solar cooker you are interested in creating, they reflect in different ways. For example, parabolic cookers use reflection of the sun into a direct point into the pot while solar kettles trap heat in a glass tube and convey the heat through the bottom of water. Solar ovens generally use the sun as a gas oven uses gas, by turning it into fuel, which burns creating heat. The same principal is applied to solar ovens. They take the sun or ‘fuel’ and use its heat to cook food. It is simply making the burning part obsolete, therefore being more environmentally friendly.

Panel cookers are fairly simple to obtain. Panel cookers are among the most popular solar cookers. They are very easy to obtain by buying them. In 1994, Solar Cookers International, or SCI, created the first production solar cooker, the CooKit. It generally costs around five US dollars. The HotPot, developed by US NGO Solar Household Energy, Inc. is a new innovation that can be used with panel cookers. It has a clear lid and can be suspended so it creates more surface area for the sun to heat and it allows users to view the food as it is prepared. As an alternative to spending money, cardboard, tin foil, and a black pot are as good as anything to create your very own panel cooker.

Solar kettles are solar thermal devices that are generally used to heat water to its boiling point so as to remove any pathogens. They are solar vacuum glass tubes with liquids, generally water, inside them. Because they work on accumulated solar energy, rather than direct solar energy, they are ideal for boiling water over night during camping trips or other outdoor adventures. Because solar vacuum glass tubes are not easy to obtain, you will have to visit a science store or online science resource to have one of these handy cookers.

Parabolic cookers have all of the cooking capabilities of a normal oven, but they can be a real nuisance to construct. They reach very high temperatures and cook quickly, but require frequent adjustment and supervision for safe operation. They are generally used for large-scale institutional cooking. Several hundred thousand of them have been distributed in China alone. The Solar Bowl is a unique technology used in Auroville, Indiana by Solar Kitchen. Unlike most heat concentrating techniques that use tracking reflector systems, the solar bowl uses a spherical reflector that makes use much less complicated. The reflector focuses the heat along a line perpendicular to the sphere’s surface and a control system moves the receiver to intersect this line. Steam is produced in the solar bowl’s receiver at temperatures reaching 150° C, thus cooking the food.

Solar box cookers use the same principal that panel cookers use, except in a more compact, portable version. They can be created in a few hours and can cook many different foods, depending on the size of box you have chosen. Because they are not a very popular branch of solar cookers, nobody has seen the potential that they have to work with. Solar box cookers can be made out of any material, preferably cardboard or a type of wood, and tin foil. Some solar box cookers can be up to five feet wide and three feet tall. These can be used to cook anything, including a Thanksgiving Turkey!

Solar energy begins in the sun. The sun produces radiant energy by consuming hydrogen in nuclear fusion reactions. Solar energy is transmitted to earth in photons, which interact with the Earth’s atmosphere and surface. It takes about 8 minutes and 20 seconds for the sun’s energy to reach the Earth. The Earth receives and collects solar energy in the atmosphere, oceans, and plant life. Interactions between the sun’s energy, the oceans, and the atmosphere, for example, create winds which can affect the type of solar cooker you would need to use. Solar cookers utilize the photons in a different way than the Earth does. The photons are reflected back into the food, creating heat, which then cooks the food.

Solar cookers don’t only benefit people in the USA. Solar cookers around the world are helping people to survive. In Africa, solar cookers are distributed to small tribes by relief funds. These solar cookers are used to cook food and pasteurize water and milk. They also help stop the spread of disease, by killing the bacteria in their food and water. In Australia, solar cookers have been used by wildlife conservationists while they are studying animals to try to keep them alive. Solar kettles have been distributed in China and have helped with hunger there. People all over the world have already integrated solar cooking into their lives. So why can’t we?

Convection is the method by which solar ovens cook food. Convection is the process of warm fluids and gasses rising and cool fluids or gasses sinking. Convection builds inside the pot when you are cooking, and the warming of the gasses is due to the sunlight directed onto it. As the cool and warm gasses begin to swirl within eachother, the warm gasses overtake the cool gasses and all of the gasses become warm. This causes the food’s temperature to rise, thus cooking it.

Solar ovens are easily built. To build the CooKit, you simply order it online and follow the instructions. But, if you would like to build your own solar cooker without ordering one, the Easy Lid solar cooker might be the right one for you. Begin by taking a large box and cut it in half. Refer to the graphics section under “construction”. Fold an extra cardboard piece so that it forms a liner around the inside of the base. Use the lid piece to mark a line around the liner. Cut along this line leaving four tabs. Glue aluminum foil to the inside of the liner and to the bottom of the outer box inside. Set a smaller box into the opening formed by the liner until the flaps of the smaller box are horizontal and flush with the top of the liner. Place some wads of newspaper between the two boxes for support. Mark the underside of the flaps of the smaller box using the liner as a guide. Fold these flaps down to fit down around the top of the liner and tuck them into the space between the base and the liner. Fold the tabs over and tuck them under the flaps of the inner box so that they obstruct the holes in the four corners. Now glue these pieces together in their present configuration. As the glue is drying, line the inside of the inner box with aluminum foil. To finish the lid, measure the width of the walls of the base and use these measurements to calculate where to make the cuts that form the reflector. Only cut on three sides. The reflector is folded up using the fourth side as a hinge. Glue an oven cooking bag or glass in place on the underside of the lid. If you are using glass, sandwich the glass using extra strips of cardboard. Allow it to dry. Bend the ends of the wire and insert these into the corrugations on the lid and on the reflector to prop open the latter paint the sheet metal (or cardboard) piece black and place it into the inside of the oven. To improve efficiency, glue thin strips of cardboard underneath the sheet metal (or cardboard) piece to elevate it off of the bottom of the oven slightly. Cut off the reflector and replace it with one that is as large as, or larger than, the entire lid. This reflects light into the oven more reliably. Turn the oven over and open the bottom flaps. Place one foiled cardboard panel into each airspace to divide each into two spaces. The foiled side should face the center of the oven.

If the EasyLid Solar Cooker wasn’t your type of solar oven, perhaps you would like to build the DSPC. This is ideal for when the sun’s altitude is very high, and trumps the CooKit in this area of solar cooking. To build it you will need a single sheet of cardboard or plastic board measuring 4′ x 3′ and aluminum foil. To build it, draw the DSPC pattern, found in the graphics section, onto a 4′ x 3′ cardboard piece. Cut along the solid lines, and fold along the dash lines. Make sure all fold lines are well folded so the cooker can freely assume its proper shape when set up. Make the center slot width equivalent to the thickness of two sheets of cardboard stacked together. Next glue on the aluminum foil and the cooker is ready for use. To improve efficiency, For low-sun altitude cooking, below 65 degrees, the two forward triangular panels, on each DSPC side wing, are placed under the trapezoidal base. In this setting, DSPC functions and performs pretty much the same as the CooKit. The forward rectangular panel can either lay flat or propped up, with a small object, for the proper reflection angle as required. For high-sun altitudes cooking, above 60 degrees, the two forward triangular panels, on each DSPC side wing, are placed over the trapezoidal base. The two small flaps will fit inside the center slot, on the forward rectangular panel, to hold the cooker shape (see photo on the right). In this setting, DSPC performs more efficiently with extra panels. If required, tying the two forward triangular flaps together with a short string will bring the two forward triangular panels even closer. To cook, first configure the DSPC according to the sun’s altitude. Face the cooker towards the sun. Put the food you wish to cook inside a black metal pot, and enclose the pot in an oven bag or a clear glass container. Place the pot in the middle of DSPC’s base. Raise the cooking pot by about two inches above the base, using trivet or wire cage, to bring the pot into the proper focus of the cooker. For high-sun altitude setting, raising the pot allows a pot with a diameter greater than 7.5 inches to be used because the added reflective panels in the front restrict space available at the base level.

As the DSPC is meant for high-altitude solar cooking, you may need a low-altitude solar cooker. The Parvati Solar Cooker, which is also a low-cost solar cooker, is a bit complicated to make. But, it is also a very successful solar cooker and has been used all over Africa for the last ten years. To build it, scientist began with the funnel solar cooker by Dr. Steven E. Jones, and built upon it. Circular Parvati Solar cooker is made of three sections. Part C forms the upper section. Part B forms the lower section and part A forms the base of the cooker. How to cut these three parts from a single sheet of cardboard or aluminum or stainless steel sheet is shown in Fig 4. Detailed dimensions for 24 inch diameter cooker are shown in Fig 5. This collector can collects heat energy equivalent to about 300 watts. For higher energy diameter of 30, 36, 48 or higher can be used. For these sized collectors multiply the given dimensions by 1.25, 1.5 or 2 respectively. Part C is semicircle shaped. Outer radius is 24 inches and inner radius is 16 inches. Join two end of this semicircle to form the upper section of cone. Part B has outer radius of 12 inches, next circle is of radius 11.3 inches and third circle of radius 4.8 inches. Part B is 255 degrees section of circle. Join two end of this section to form the middle section of cone. Part B has collar space to join it to Part C. Part A is base of the structure. It is made of circle of radius 4.0 inches. There is another circle seen inside with same center. Its radius is 3.6 inches. This collar space is for joining the base to part B. The construction is shown Fig 6. Small V-cuts are to be made in collar space of Part B and Part A. Then bend these V-cuts on inside. This will make it easy to join together the parts together this is shown in Fig 6. To make the structure sturdy and durable we have pasted brown paper on external surface of the cooker. After pasting the paper we have found the structure became stiff and does not need any support. Since Parvati solar cooker is modified version of funnel cooker its use is identical. We have used a metallic stand to place the conical reflector. Another small tripod stand is used to place the cooking pot. As stated earlier we are using three pots in stacked position to cook the food. To retain the heat plastic cover is used. Instead of directly placing the plastic cover a small metallic stand is made and plastic bag is fitted onto it. This cover is sufficiently big so that is does not touching the cooking pots. An arrangement is made for focusing. Instead of a focusing pin a simple arrangement can be substituted. On a small metallic plate fixed to the rim of reflector a Nut bolt of 1/4 inch diameter and two inch long is fixed with two round washers at two ends. When the cooker is properly focused the shadow of the upper washer coincides with the washer on the metal plate. While focusing it is better to adjust position in such a way that shadow of upper washer is slightly on the west so that sun tracking error is taken care of.
Solar ovens, no matter what type and where you use them, need the sun. On cloudy days or under a canopy, there actually is a way to substitute for the sun. UV light bulbs do not require gas. They put out enough wattage, when focused in the right area, to cook food in about an hour and a half. To use this procedure, simply use a rechargeable battery and 3 handheld UV lights positioned in a triangular formation and aim them facing right in-between the stand of the next light and the pot in the center of the solar oven. You may have to bring several rechargeable batteries with you, however, because most batteries will run a UV lamp for about an hour.

Solar ovens can save the US from their gas crisis, while helping the environment, the ozone layer, and the economy. They are fairly cheap to purchase or build, and can be made out of several household items. So, please, do the world a favor and go get a solar oven.